Wheww! I really wish you had broken this up into more manageable
packets and sent them one at a time!
(1) Everytime I am reminded of these "are brains necessary" examples, I
resolve to look more closely at evidence for "normality", and evidence
re what is or is not intact--regrettably, I am caught unprepared oone
more time. I will point out, however, that it has long been known that
hydrocephalic children with superficially normal behavior may show
deficits when examined neuropsychologically--for example, in subtle
language deficit alluded to in the expression "cocktail party speech"
(i.e. "correct" but rather empty), and in some visual-spatial problems
(e.g. constructional apraxia).
Same likely to be true with early hemispherectomy, I believe.
Still, to have any function at all with extreme anatomical abnormality
is remarkable, and does attest to difference between atypical
development and loss of structures after normal development.
re emotional anomalies if limbic connections damaged: how much do we
know about emotional status of specific cases? Might they be better
tolerated among mathematicians than in soome other groups and hence
escape mention?
re capacity to achieve "consciousness"--lacking a definition, don't
know, but I am struck by the ability of blind/deaf people (e.g. Helen
Keller) to achieve communication; ditto re-invention of (sign) language
by pairs of deaf children (for communication with each other).
(2) I am embarassed to hear of that "psychologist" saying the brain is
just 500% fat...
F. LeFever
New York Neuropsychology Group
In <6p66cc$mbg$1 at hermes.bit.net.au> "Rugrat"
<johnhkm at logicworld.com.au> writes:
>> 22/07/98 23:31
>>Help.
>>Over recent years there have been many significant advances in the
>neurosciences but it seems to me that there still must be drawn a
sharp
>distinction between the findings of neuroscience, presently at least,
and
>the nature of human consciousness. No surprise there, but it irritates
me.
>>Many years ago I saw a BBC special in which they interviewed a number
of
>adults (ages 18 -25) who had developed hydrocephalus as children and
had a
>shunt installed. Performing CAT scans (I think) the researchers
established
>that a few of these individuals had suffered significant tissue loss
due to
>shunt failure. One of the students, a 21 year old honours math student
at
>Birmingham University (I think, it was over 7 years ago), had less
than half
>or third of the typical neocortex; although he did have a very rich
blood
>supply to the remaining regions(signficant).
>>The CAT scans were fascinating as the tissue loss was obvious. I
mentioned
>this to a psychologist once who tepidly replied, "Well, the brain is
50%
>fat." The tissue loss involves both grey and white matter.
Mylineation,
>important stuff, irrelevant. The issue is that there must have been a
major
>disruption of the internal pathways, although I doubt the corpus
callosum
>was damaged too much. Another consideration here is that 3 significant
(two
>specialised) pathways only on the left hemi, the superior longitudinal
>fasciculus, the arcuate fasciculus, and the angular gryus, were also
>probably spared, but many thalamic connections and nuclei were
involved, and
>also the frontal lobe-limbic (mesocortical?) connections were probably
>damaged. Given this and the likely limbic disruptions
>(hippocampus\amgydala?) I thought emotional anomalies would be
prevalent
>amongst such patients.
>>The damage is gradual, and experiments have confirmed that a number of
small
>lesions is much less damaging than a single large lesion, the
hypothesis
>being that the brain can cope with the little disasters but is
overwhelmed
>by the quick big one. There is evidence of stem and glial cell
migration to
>damaged areas. The problem in the above and other individuals is that
>sometimes the entire structure is gone, or at least incapable of being
>identified in these 'reconstituted' brains.
>>Interesting I thought but it was a TV progam after all. Norman Cook,
"The
>Brain Code: Mechanisms of Information Transfer Across the Corpus
Callosum",
>makes mention of such anomalies and makes reference to their
disturbing
>implications. Over the last few months more evidence, postings by
doctors
>(Anthro L, good archived discussion on it) who have witnessed similiar
and
>expressed some astonishment. I accept the reality that there are some
normal
>people who by most current understandings should be dithering
emotionally
>unpredictable unconscious automatons.
>>Given that in hominid evolution a great deal is made about the slowly
>increasing cerebral volume I find such examples frustrating. It does
seem
>that we are developing a reasonable grasp on how normal brains develop
but
>when there is early childhood pathology the brain undertakes novel
>strategies to achieve its goals. In some cases it does this
exceptionally
>well.
>>It is as if the human brain, at a cellular level, or by some
internally
>driven organisational level (hox genes? timeframes out?, modular,
surviving
>neurons [cf possible blindsight explanation],
>stimulus\topographical\symbolic processing,) is destined to achieve
>consciousness by whatever means. How's that for metaphysical. The
early
>childhood is very significant though, that's when real recovery can
occur. I
>have noted some studies indicating that children who suffered from
cerebral
>injury leading to asphasia, while often demonstrating an apparent full
>recovery, do display subtle signs of the old injury. And many people
with
>seemingly normal brains just aint that.
>>A possible escape ...
>>In one of the above examples I made reference to the rich blood supply
to
>the remaining tissue. In hydrocephalics the damage, I believe, is
inside
>out, the arterial network may remain relatively intact, and given the
>incredible plasticity of brain blood supply, it is conceivable that
the
>remaining tissues receive a larger blood dose and so are are able to
operate
>at an optimium level. It would be interesting to know if the current
blood
>supply arrangements for the normal human brain are 'stretched to the
limit'.
>Not meaning to sound sinister, but I wonder if these cerebrally
deprived
>individuals will be more likely to develop dementia through redundancy
loss,
>or at earlier ages. Do they suffer any volume shrinkage with age as
the
>normal brain does?
>>The problem for human brains may be that of supply and demand, even
though
>it already consumes 20% of everything @ 2% bodyweight it wants more or
at
>least could work a whole lot better if it had more. Intravenous
glucose
>injection provides an immediate IQ boost. Brain cell genes are also
the most
>expressive in the human body, neurones are metabolically manic. Recent
>treatments for dementia etc have focussed on increasing oxygen supply
to the
>brain. In one study many years ago oxygen enhancement was shown to
>significantly increase performance, but then lots of things seem to do
that.
>This supports an ongoing mild nutrient deprivation idea.
>>Our cortices may have outgrown our heart, which has to work so hard to
pump
>the blood up there. Bipedalism aint that old and we possess relatively
huge
>brains. How would a giraffe manage with a similiar brain\bodyweight?
The
>existing system suggests that evolution has already gone to a great
deal of
>trouble to feed this hungry organ; an organ capable of generating its
own
>hunger. The brain is vulnerable to malnutrition, especially during
early
>childhood.
>>This is one way out of the problem, but it does suggest that the
>evolutionary mechanisms governing our cerebral construction are
somewhat out
>of step. This explains human history. It also allows the possibility
that
>significant increases in brain function are possible; although only
through
>some physical and\or genetic re-arrangement of bloody supply
mechanisms at a
>young age, an unpleasant prospect.
>>The above argument is also applicable to the question of brain
cooling. "The
>Radiator Hypothesis" is a possible explanation for the rapid
encephalization
>of the hominid line. Its basic premise is that the intricate bloody
supply
>system also serves as a brain cooling system and walking on those hot
>African savannas made brains hot. Some larger African predators will
not
>hunt in the heat of the day; their metabolism isn't up to it. Maybe it
just
>gets too hot up there sometimes.
>>To steal Restak's title, The brain does have a mind of its own, even
before
>it has what we recognize as a mind it is heading towards creating one
by
>hook or by crook. If something gets in the way it seems capable of
invoking
>a set of hidden (?) strategies to find novel ways to achieve its goal.
>Brains aren't following our rules, they create the rules. I wonder if
>Neuroscience is faced with the unfortunate prospect of delineating how
>brains work by the history of each brain(or categories of), which
implies
>that no single theoretic construction will be sufficient to fully
explain
>how all brains do what they do.
>>An 'information processing' model may avoid this problem, but I
perceive
>this as a type of dualism unless the model's units are
neuroanatomical,
>which is a problem with the hydrocephalics. The other thought here is
that
>each 'type' of brain may have its own type of basic information unit.
(I
>don't think so though. Epistemologically terrifying.) The firings may
be the
>same, but individuals may report different experiences for the same
neural
>events. I believe studies have been conducted demonstrating such
anomalies
>in self-reporting.
>>Neurosurgeons report that each brain is unique, each constructed
slightly
>and not so slightly differently. (Which may explain above anomaly re
self
>report.) Consciousness is very old, not requiring a massive neocortex
at
>all, just a well fed one, particularly if you're on four legs and
>horizontal; or a sea mammal. There have been some animal studies
lately
>which have strongly suggested (satisfactorily in my opinion) that a
>signficant number of mammals possess a style of consciousness, that
while
>different from our own, is nonetheless probably conscious at the
>experiential level. Now, where are those crystals ... . Someone please
take
>these dreams away. I'll stop because I need help.
>>Any assistance appreciated.
>>>Rugrat
>johnhkm at logicworld.com.au>>>>>>>>>